1. Field of Invention
The field of the currently claimed embodiments of this invention relates to optical coherence tomography (OCT) systems, and more particularly to real-time 3D and 4D Fourier domain Doppler optical coherence tomography systems.
2. Discussion of Related Art
Optical coherence tomography (OCT) is a well-established, non-invasive optical imaging technology that can provide high-speed, high-resolution, three-dimensional images of biological samples. Since its invention in the early 1990s, OCT has been widely used for diagnosis, therapy monitoring, and ranging [1]. In vivo non-invasive imaging of both microcirculation and tissue structure is a hot area that has attracted significant amounts of interest since it is an indicator of biological functionality and abnormality of tissues. Pioneering work by Z. P. Chen et al. combining the Doppler principle with OCT has enabled high resolution tissue structure and blood flow imaging [2]. Since then, OCT-based flow imaging techniques have evolved into two different approaches: optical coherence angiography (OCA) to detect microvasculature [3-7] and Doppler tomography (ODT) to quantitatively measure blood flow [8-15]. In spectral domain ODT, the magnitude of Fourier transformation of the spectral interference fringes is used to reconstruct cross-sectional, structural image of the tissue sample, while the phase difference between adjacent A-scans is used to extract the velocity information of the flow within the tissue sample [2,8].
Real-time imaging of tissue structure and flow information is always desirable and is becoming more urgent as fast diagnosis, therapeutic response, and intraoperative OCT image-guided intervention become established medical practices. Due to the large amount of raw data generated by an OCT engine during a high-speed imaging process and heavy computation task for computer systems, real-time display is highly challenging. A graphics processing unit (GPU)-accelerated signal-processing method is a logical solution to this problem due to the way OCT data are acquired and due to the fact that they can be processed in parallel. Although researchers have reported a number of studies using GPU to real-time process and display OCT images [16-25], reports of real-time functional OCT imaging based on GPU processing—which is highly demanding and would be of great value for medical and clinical applications—have been uncommon. GPU-based speckle variance swept-source OCT (SS-OCT) [24] and 2D spectral domain Doppler OCT (SD-DOCT) [25] have recently been reported. There thus remains a need for improved OCT systems.